(a) Field of the Invention
The present invention relates to a monitoring device and method to detect an abnormal switching operation. Particularly, the present invention relates to a monitoring device to monitor non-zero voltage switching and a non-zero voltage switching method.
(b) Description of the Related Art
It is preferable that a MOSFET switch controlling an operation of a converter is controlled in order to operate with zero voltage switching. The switching loss is reduced and damage to the switch can be prevented under the condition of the zero voltage switching. The zero voltage switching means that a voltage at both ends of the switch is “0” at the turn-on time of the switch,
For example, in case of a LLC resonant converter, when an overload is applied or an input voltage is low, a phase of a drain current of the MOSFET switch precedes a phase of a gate input signal. Then, a hard switching and a shoot-through phenomenon are generated in switching operations of the switch.
The hard switching is a phenomenon in which it is turned on before the voltage at both ends of the switch falls down “0”. The shoot-through is the phenomenon in which a high peak current flows through the switch by a reverse recovery of a body diode. Such phenomenon increases the switching loss. In addition, it causes the switch to be damaged.
Accordingly, in case the switching when failing in the zero-voltage switching, that is, when the non-zero voltage switching occurs, a power consumption increase by switching loss and switch damage is caused.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.